I n 1977, the physicist Freeman Dyson published the first of a series of articles about how plants affect the planet’s carbon-dioxide concentrations. Every summer, plants absorb about a tenth of the carbon dioxide in the atmosphere. In the fall, when they stop growing or shed their leaves, they release most of it back into the air. Dyson proposed creating forests of “carbon-eating trees,” engineered to suck carbon more ravenously from the air, and to keep it tied up in thick roots that would decay into topsoil, trapping the carbon. He now estimates that by annually increasing topsoil by just a tenth of an inch over land that supports vegetation, we could offset all human carbon emissions.
Dyson’s early geo-engineering vision addressed a central, and still daunting, problem: neither sulfur-aerosol injection nor an armada of cloud whiteners nor an array of space-shades would do much to reduce carbon-dioxide levels. As long as carbon emissions remain constant, the atmosphere will fill with more and more greenhouse gases. Blocking the sun does nothing to stop the buildup. It is not even like fighting obesity with liposuction: it’s like fighting obesity with a corset, and a diet of lard and doughnuts. Should the corset ever come off, the flab would burst out as if the corset had never been there at all. For this reason, nearly every climate scientist who spoke with me unhesitatingly advocated cutting carbon emissions over geo-engineering.
But past international efforts to reduce emissions offer little cause for optimism, and time may be quickly running out. That’s why a few scientists are following Dyson’s lead and attacking global warming at its source. David Keith, an energy-technology expert at the University of Calgary, hopes to capture carbon from the air. He proposes erecting vented building-size structures that contain grids coated with a chemical solution. As air flows through the vents, the solution would bind to the carbon-dioxide molecules and trap them. Capturing carbon in these structures, which might resemble industrial cooling towers, would allow us to manage emissions cheaply from central sites, rather than from the dispersed places from which they were emitted, such as cars, planes, and home furnaces. The grids would have to be scrubbed chemically to separate the carbon. If chemists could engineer ways to wash the carbon out that didn’t require too much energy, Keith imagines that these structures could effectively make our carbon-spewing conveniences carbon-neutral.
The question then becomes where to put all that carbon once it’s captured. Keith has investigated one elegant solution: put it back underground, where much of it originated as oil. The technology for stashing carbon beneath the earth already exists, and is routinely exploited by oil-well drillers. When oil wells stop producing in large quantities, drillers inject carbon dioxide into the ground to push out the last drops. If they inject it into the right kind of geological structure, and deep enough below the surface, it stays there.
We might also store carbon dioxide in the oceans. Already, on the oceans’ surface, clouds of blooming plankton ingest amounts of carbon dioxide comparable to those taken in by trees. Climos, a geo-engineering start-up based in San Francisco, is trying to cultivate ever-bigger plankton blooms that would suck in huge supplies of carbon. When the plankton died, the carbon would end up on the sea floor. Climos began with the observation that plankton bloom in the ocean only when they have adequate supplies of iron. In the 1980s, the oceanographer John Martin hypothesized that large amounts of oceanic iron may have produced giant plankton blooms in the past, and therefore chilled the atmosphere by removing carbon dioxide. Spread powdered iron over the surface of the ocean, and in very little time a massive bloom of plankton will grow, he predicted. “Give me half a tanker of iron,” Martin said, “and I’ll give you the next Ice Age.” If Martin’s ideas are sound, Climos could in effect become the world’s gardener by seeding Antarctic waters with iron and creating vast, rapidly growing offshore forests to replace the ones that no longer exist on land. But this solution, too, could have terrible downsides. Alan Robock, an environmental scientist at Rutgers, notes that when the dead algae degrades, it could emit methane—a greenhouse gas 20 times stronger than carbon dioxide.
Just a decade ago, every one of these schemes was considered outlandish. Some still seem that way. But what sounded crankish only 10 years ago is now becoming mainstream thinking. Although using geo-engineering to combat climate change was first considered (and dismissed) by President Johnson’s administration, sustained political interest began on the business-friendly right, which remains excited about any solution that doesn’t get in the way of the oil companies. The American Enterprise Institute, a conservative think tank historically inimical to emission-reduction measures, has sponsored panels on the sulfur-aerosol plan.
By now, even staunch environmentalists and eminent scientists with long records of climate-change concern are discussing geo-engineering openly. Paul Crutzen, who earned his Nobel Prize by figuring out how human activity punched a hole in the ozone layer, has for years urged research on sulfur-aerosol solutions, bringing vast credibility to geo-engineering as a result.
With that growing acceptance, however, come some grave dangers. If geo-engineering is publicly considered a “solution” to climate change, governments may reduce their efforts to restrict the carbon emissions that caused global warming in the first place. If you promise that in a future emergency you can chill the Earth in a matter of months, cutting emissions today will seem far less urgent. “Geo-engineering needs some government funding, but the most disastrous thing that could happen would be for Barack Obama to stand up tomorrow and announce the creation of a geo-engineering task force with hundreds of millions in funds,” says David Keith.
Ken Caldeira, of the Carnegie Institution for Science, thinks we ought to test the technology gradually. He suggests that we imagine the suite of geo-engineering projects like a knob that we can turn. “You can turn it gently or violently. The more gently it gets turned, the less disruptive the changes will be. Environmentally, the least risky thing to do is to slowly scale up small field experiments,” he says. “But politically that’s the riskiest thing to do.”
Such small-scale experimentation, however, could be the first step on a very slippery slope. Raymond Pierrehumbert likens geo-engineering to building strategic nuclear weapons. “It’s like the dilemma faced by scientists in the Manhattan Project, who had to decide whether that work was necessary or reprehensible,” he says. “Geo-engineering makes the problem of ballistic-missile defense look easy. It has to work the first time, and just right. People quite rightly see it as a scary thing.”
T he scariest thing about geo-engineering, as it happens, is also the thing that makes it such a game-changer in the global-warming debate: it’s incredibly cheap. Many scientists, in fact, prefer not to mention just how cheap it is. Nearly everyone I spoke to agreed that the worst-case scenario would be the rise of what David Victor, a Stanford law professor, calls a “Greenfinger”—a rich madman, as obsessed with the environment as James Bond’s nemesis Auric Goldfinger was with gold. There are now 38 people in the world with $10 billion or more in private assets, according to the latest Forbes list; theoretically, one of these people could reverse climate change all alone. “I don’t think we really want to empower the Richard Bransons of the world to try solutions like this,” says Jay Michaelson, an environmental-law expert, who predicted many of these debates 10 years ago.